Combination eas and rfid label or tag using a hybrid rfid antenna

ABSTRACT

A security tag includes an EAS component having a defined surface area, and an RFID component having a defined surface area. The EAS component surface area is configured to at least partially overlap the RFID component surface area. The RFID component includes an antenna which at least partially overlaps the first surface. A substantially planar spacer having a thickness is at least partially disposed between the defined surface areas of the EAS and RFID components. The RFID element read range is affected and controlled by the spacing between the RFID element and the EAS element. The RFID reader is capable of activating the RFID component when the RFID component is within the read range. The antenna includes a magnetic loop antenna in electrical contact with a spiral antenna to increase near field read response.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation-in-Part Application of U.S. NationalStage application Ser. No. 11/667,743, filed May 14, 2007, entitledCOMBINATION EAS AND RFID LABEL OR TAG, based on PCT Application NumberPCT/US2005/041573, filed Nov. 15, 2005, entitled COMBINATION EAS ANDRFID LABEL OR TAG which is related to and claims priority to U.S.Provisional Application Ser. No. 60/628,303, filed Nov. 15, 2004,entitled COMBO EAS/RFID LABEL OR TAG, the entirety of which all areincorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

n/a

FIELD OF THE INVENTION

The present disclosure relates to an electronic article surveillance(EAS) label or tag for the prevention or deterrence of unauthorizedremoval of articles from a controlled area. More particularly, thepresent disclosure relates to an EAS label or tag combined with aradiofrequency identification (RFID) label or tag for recordation ofdata specific to the article and a novel RFID label or tag, where theRFID tag includes an RFID hybrid antenna inlay having both a spiralantenna and a magnetic loop antenna.

BACKGROUND OF THE INVENTION

Electronic article surveillance (EAS) systems are generally known in theart for the prevention or deterrence of unauthorized removal of articlesfrom a controlled area. In a typical EAS system, EAS markers (tags orlabels) are designed to interact with an electromagnetic field locatedat the exits of the controlled area, such as a retail store. These EASmarkers are attached to the articles to be protected. If an EAS tag isbrought into the electromagnetic field or “interrogation zone,” thepresence of the tag is detected and appropriate action is taken, such asgenerating an alarm. For authorized removal of the article, the EAS tagcan be deactivated, removed or passed around the electromagnetic fieldto prevent detection by the EAS system.

EAS systems typically employ either reusable EAS tags or disposable EAStags or labels to monitor articles to prevent shoplifting andunauthorized removal of articles from the store. The reusable EAS tagsare normally removed from the articles before the customer exits thestore. The disposable tags or labels are generally attached to thepackaging by adhesive or are located inside the packaging. These tagstypically remain with the articles and must be deactivated before theyare removed from the store by the customer. Deactivation devices may usecoils which are energized to generate a magnetic field of sufficientmagnitude to render the EAS tag inactive. The deactivated tags are nolonger responsive to the incident energy of the EAS system so that analarm is not triggered.

For situations where an article having an EAS tag is to be checked-in orreturned to the controlled area, the EAS tag must be activated orre-attached to once again provide theft deterrence. Because of thedesirability of source tagging, in which EAS tags are applied toarticles at the point of manufacturing or distribution, it is typicallypreferable that the EAS tags be deactivatable and activatable ratherthan be removed from the articles. In addition, passing the articlearound the interrogation zone presents other problems because the EAStag remains active and can interact with EAS systems in other controlledareas inadvertently activating those systems.

Radio-frequency identification (RFID) systems are also generally knownin the art and may be used for a number of applications, such asmanaging inventory, electronic access control, security systems, andautomatic identification of cars on toll roads. An RFID system typicallyincludes an RFID reader and an RFID device. The RFID reader may transmita radio-frequency carrier signal to the RFID device. The RFID device mayrespond to the carrier signal with a data signal encoded withinformation stored by the RFID device.

While the use of a spiral antenna alone has its benefits, the couplingmechanism depends mainly on the electric E field and not the magnetic Hfield. In some instances, the overall RFID read performance is optimizedfor the far field and the resulting near field read performance may belimited. That is, the antenna cannot be optimized for both the far fieldand near field. The near field performance depends on how the antennawas designed for the far field. For combination EAS/RFID tagapplications, a spiral antenna may limit the various options for nearfield antennas used in detachers and other POS applications where closeproximity read performance is especially important.

The open antenna structure of a spiral antenna allows low frequency orstatic electric E field to develop a substantial voltage across the RFIDchip and this can cause failure of the device if the level is highenough. Such ESD (electrostatic discharge) can occur in the processes oflabel manufacturing or ultrasonic welding of the hard tag housing.

The market need for combining EAS and RFID functions in the retailenvironment is rapidly emerging. Many retail stores that now have EASfor shoplifting protection rely on bar code information for inventorycontrol. RFID offers faster and more detailed inventory control over thebar code. Retail stores already pay a considerable amount for hard tagsthat are re-useable. Adding RFID technology to EAS hard tags couldeasily pay for the added cost due to improved productivity in inventorycontrol as well as loss prevention.

What is therefore needed is an RFID antenna design for use in anEAS/RFID interrogation system that increases near field read performancewithout sacrificing far field read performance, while at the same timereducing the likelihood of chip failure due to the build up ofelectrostatic discharge.

SUMMARY OF THE INVENTION

The present invention advantageously provides a tag or label which inone tag or label combines the features of an independent EAS tag orlabel and an independent RFID tag or label.

More particularly, the present disclosure relates to a security tagwhich includes an EAS component having a defined surface area, and anRFID component having a defined surface area. The defined surface areaof the EAS component is configured to at least partially overlap thedefined surface area of the RFID component.

The present disclosure provides a security tag that includes an EAScomponent having a defined surface area, and an RFID component having adefined surface area. The EAS component surface area is configured to atleast partially overlap the RFID component surface area. The RFIDcomponent includes an antenna which at least partially overlaps thefirst surface. A substantially planar spacer having a thickness is atleast partially disposed between the defined surface areas of the EASand RFID components. The RFID element read range is affected andcontrolled by the spacing between the RFID element and the EAS element.The RFID reader is capable of activating the RFID component when theRFID component is within the read range. The antenna includes a magneticloop antenna coupled to a spiral antenna to increase near field readresponse.

The RFID component includes an antenna and the antenna may at leastpartially overlap the defined surface area of the EAS component. Asubstantially planar spacer having a thickness may be at least partiallydisposed between the defined surface area of the EAS component and thedefined surface area of the RFID component. The thickness of the spacerdetermines a read range between an RFID reader and the RFID component,and the RFID reader is capable of activating the RFID component when theRFID component is within the read range. The antenna and the EAScomponent may form a part of an impedance matching network of theantenna. The antenna impedance may include loading effects of the EAScomponent. The RFID component may include the antenna and an applicationspecific integrated circuit (ASIC). The ASIC may have a compleximpedance. The complex impedance of the ASIC may match a coupled complexconjugate impedance of the antenna including the loading effects of theEAS component. A material for a base portion of the RFID component maybe selected from the group consisting of (a) base paper, (b)polyethylene, (c) polyester; (d) polyethyleneterephthalate (PET); and(e) polyetherimide (PEI). The base portion material may be plastichaving a dielectric constant of about 3.3 and a loss tangent of lessthan about 0.01. The spacer material may be selected from the groupconsisting of (a) a low loss, low dielectric material; and (b) air.

The present invention relates also to a method of operating acombination of an electronic article surveillance (EAS) component and aradiofrequency identification (RFID) component. The method includes thestep of moving the RFID component to be overlapped by the EAS componentso as to change the impedance of an antenna coupled to the RFIDcomponent. The impedance of the antenna includes the loading effects ofthe EAS component. The antenna may include an antenna conductor and theantenna is tuned by severing the antenna conductor into at least twosegments such that at least one segment point corresponds to anoperating frequency for the antenna based upon the length of the atleast two antenna segments, and isolating the severed antenna conductorfrom remaining portions of the conductor.

The method may further include the combination of an electronic articlesurveillance (EAS) component and a radiofrequency identification (RFID)component having a spacer disposed therebetween, with the spacer havinga thickness, and the method may include the step of varying thethickness of the spacer. The step of varying the thickness of the spacermay vary a read range between an RFID reader and the RFID component, andwherein the RFID reader is capable of activating the RFID component whenthe RFID component is within the read range.

In another embodiment, a security tag is provided, where the tagincludes an electronic article surveillance (EAS) component having afirst defined surface area and a radiofrequency (RFID) component havinga second defined surface area. The RFID component includes a hybridantenna inlay having an inward spiral antenna, a magnetic loop antennain electrical contact with the spiral antenna, an integrated circuit inelectrical contact with the magnetic loop antenna.

In yet another embodiment, an RFID antenna inlay for use with acombination EAS/RFID security tag is provided. The antenna inlayincludes an inward spiral antenna having a first section and a secondsection, a magnetic loop antenna in electrical contact with the spiralantenna and being positioned between the first section of the spiralantenna and the second section of the spiral antenna, and an integratedcircuit in electrical contact with the magnetic loop antenna.

In still another embodiment, a method for providing an enhanced readresponse for a security tag is provided. The method includes providingan electronic article surveillance (EAS) component having a firstdefined surface area, and positioning a radiofrequency (RFID) componenthaving a second defined surface area to at least partially overlap theEAS component. The RFID component includes a hybrid antenna inlay, wherethe antenna inlay includes an inward spiral antenna, a magnetic loopantenna in electrical contact with the spiral antenna, an integratedcircuit in electrical contact with the magnetic loop antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the embodiments is particularly pointedout and distinctly claimed in the concluding portion of thespecification. The embodiments, however, both as to organization andmethod of operation, together with objects, features, and advantagesthereof, may best be understood by reference to the following detaileddescription when read with the accompanying drawings in which:

FIG. 1 illustrates a combination EAS/RFID security tag according to oneembodiment of the present disclosure;

FIG. 2A illustrates one part of sample testing data for a combinationEAS/RFID security tag according to one embodiment of the presentdisclosure;

FIG. 2B illustrates another part of sample testing data for acombination EAS/RFID security tag according to one embodiment of thepresent disclosure;

FIG. 3A illustrates an RFID system using magnetic field coupling inaccordance with one embodiment of the present disclosure;

FIG. 3B illustrates an RFID system using electric field coupling inaccordance with one embodiment of the present disclosure;

FIG. 4 illustrates a perspective exploded view of a security tag inaccordance with one embodiment of the present disclosure;

FIG. 5 illustrates a top view of the security tag of FIG. 4;

FIG. 6 illustrates a top view of a security tag with an antenna havingsegment points in accordance with an alternate embodiment of the presentdisclosure;

FIG. 7 illustrates a block flow diagram in accordance with oneembodiment of the present disclosure;

FIG. 8A illustrates a prior art configuration of a co-planar EAS labeladjacent to an RFID label;

FIG. 8B illustrates a prior art configuration of a co-planar EAS labeland an RFID label which are separated by a gap;

FIG. 8C illustrates an embodiment of the present disclosure of acombination EAS component with an RFID component mounted directlyunderneath the EAS component;

FIG. 8D illustrates an embodiment of the present disclosure of oneportion of a security tag combination EAS component with an RFIDcomponent insert;

FIG. 8E is an elevation view of the embodiment of the present disclosureof FIG. 8D;

FIG. 8F illustrates an embodiment of the present disclosure of oneportion of a security tag combination EAS component with an RFIDcomponent insert;

FIG. 8G is an elevation view of the embodiment of the present disclosureof FIG. 8F;

FIG. 9 illustrates an embodiment of the present disclosure of acombination EAS/RFID tag with a hybrid antenna inlay using a loopantenna between two inward spiral antennas;

FIG. 9A illustrates sample test data for the read range of the securitytag with hybrid antenna inlay of FIG. 9 as a function of the thicknessof a spacer between EAS and RFID components of the security tag; and

FIG. 9B illustrates the hybrid antenna inlay embodiment of FIG. 9 withthe respective response regions of the loop and spiral antennas.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure will be understood more fully from the detaileddescription given below and from the accompanying drawings of particularembodiments of the invention which, however, should not be taken tolimit the invention to a specific embodiment but are for explanatorypurposes.

Numerous specific details may be set forth herein to provide a thoroughunderstanding of a number of possible embodiments of a combinationEAS/RFID tag incorporating the present disclosure. It will be understoodby those skilled in the art, however, that the embodiments may bepracticed without these specific details. In other instances, well-knownmethods, procedures, components and circuits have not been described indetail so as not to obscure the embodiments. It can be appreciated thatthe specific structural and functional details disclosed herein may berepresentative and do not necessarily limit the scope of theembodiments.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. For example, some embodimentsmay be described using the term “connected” to indicate that two or moreelements are in direct physical or electrical contact with each other.In another example, some embodiments may be described using the term“coupled” to indicate that two or more elements are in direct physicalor electrical contact. The term “coupled,” however, may also mean thattwo or more elements are not in direct contact with each other, but yetstill co-operate or interact with each other. The embodiments disclosedherein are not necessarily limited in this context.

It is worthy to note that any reference in the specification to “oneembodiment” or “an embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment. The appearances of the phrase“in one embodiment” in various places in the specification are notnecessarily all referring to the same embodiment.

Turning now to the details of the present disclosure, one manner inwhich a combination EAS/RFID label (or tag) may be utilized is to putboth the EAS related components together with the RFID relatedcomponents and package them together. However, there may be someelectrically or electro-mechanical interacting factors that may affectthe performance of either the EAS function and/or the RFID function.Placing the RFID label on top of the EAS label is the most convenientway but may result in substantial de-tuning and signal loss for the RFIDlabel. For example, in a typical RFID device, performance of the RFIDlabel is typically very sensitive to impedance matching of anapplication specific integrated circuit (ASIC)/lead frame assembly forthe RFID device to the effective impedance of an RFID antenna mounted ona substrate. A more detailed description of some possible embodiments ofthe RFID portion of the device is discussed further below. Other objectssurrounding the RFID label may contribute to either the effectiveimpedance or the absorption of electromagnetic energy used to read theRFID label.

Some existing 2450 MHz EAS/RFID combination labels have used aconfiguration where an RFID label and an EAS label are placed in anoverlapped configuration. There may be considerable degradation in RFIDlabel detection with this particular application. Although end-to-end orslight overlap has worked best in such systems, the tag size tends tobecome prohibitively large in these instances. Also, a side-by-sideconfiguration has been known to create an irregular RFID detectionpattern. There are not many designs which have been able to successfullyimplement a combination EAS/RFID tag in the marketplace. Mostapplications using combined EAS and RFID of tagged items use separateEAS and RFID labels that are mounted separately so that they occupyconsiderable space on the tagged item than either one would occupy byitself if mounted separately.

It is envisioned that the solution to this problem is the use of an EASlabel portion of the combination tag as part of the impedance matchingnetwork for the RFID label. For example, as the RFID label is placedcloser and closer to the EAS label, the RFID label antenna impedance isaffected, or tuned, by the EAS label. In order to achieve RFID labelimpedance matching, the RFID antenna geometry may itself be designed sothat any resulting electrical effect of the EAS label on the impedanceis taken into account. For example, the RFID antenna may be configuredto have a highly capacitive impedance and which may be grosslymismatched to the impedance of the logic chip for the device (e.g., anASIC/lead frame assembly as referred to above). As the RFID label isplaced proximate the EAS label e.g., directly underneath, the impedanceof the RFID antenna is nearly matched to the ASIC impedance.

FIG. 1 generally illustrates an EAS component 1 and an RFID component 2.The EAS component 1 is an EAS label or tag. EAS component 1 may contain,for example but is not limited to, a magnetic resonator element alongwith a bias magnet (or other EAS type resonant circuits) that iscontained in a housing of plastic or some other material. Other EASlabels or tags not specifically disclosed herein may perform thefunction of EAS component 1. The RFID component 2 is an RFID label ortag. RFID component 2 may contain, for example and is not limited to,and for the purposes of discussion of FIG. 1, an antenna mounted on asubstrate material with an ASIC based RFID logic circuit or processingchip attached to the antenna, as best shown in FIG. 4 discussed below.Other RFID labels or tags not specifically disclosed herein may performthe function of RFID component 2. In one particularly useful embodiment,the RFID portion of the system, i.e., RFID component 2, operates in the868 MHz and/or 915 MHz ISM bands. Those of ordinary skill in the artwill readily appreciate, however, that the invention is not limitedthereto and may be used at any other usable frequencies.

When the EAS component 1 and the RFID component 2 are disposed adjacentone another as shown in position “P1” of FIG. 1, there is only a smalleffect of the EAS component 1 on the antenna impedance of RFID component2. However, as the RFID-component 2 is positioned underneath the EAScomponent 1 as shown in position “P2”, “P3” and “P4”, i.e., the extentof the overlap shown via a shaded area 3, the RFID antenna impedance isprogressively affected.

More particularly, the label positions P1-P4 of the RFID component 2were configured as follows:

P1=EAS component 1 and RFID component 2 disposed adjacent to each other;P2=RFID component 2 is disposed ¼ the way across and underneath theEAS-component 1; P3=RFID component 2 is disposed ½ the way across andunderneath the EAS component 1; and

P4=RFID component 2 is disposed directly underneath the EAS component 1.

For example, FIGS. 2A and 2B show test results of the real and imaginarycomponents of the RFID antenna impedance vs. frequency over the 915 MHzISM band for a sample security tag which includes EAS component 1 andRFID component 2.

As shown in. FIG. 2A, at the center frequency of 915 MHz, the realimpedance R varies from R1=about 6 ohms to R4=about 13 ohms as the RFIDlabel 2 moves from the position P1 to position P4. This apparentincrease in the real impedance R represents the effective loss increasedue to the EAS label materials. Correspondingly, the imaginary impedanceZ changes from Z1=−125 ohms to Z4=+195 ohms as the RF1-label 2 movesfrom position P1 to position P4. Therefore the imaginary impedance Zchanges from somewhat capacitive nature to inductive nature.

The RFID component 2 may be designed so that the antenna impedance isapproximately the complex conjugate of the ASIC device. This results inresonance at a target frequency, such as 915 MHz for example. Typicaltest results for the impedance of the ASIC RFID devices for chips madeby ST Microelectronics of Geneva, Switzerland with lead frame used inthis example are 5−j 140 ohms, and for chips made by Koninklikje PhilipsElectronics N.V. of Amsterdam, the Netherlands, with lead frame used inthis example, are 20−j 270 ohms. It was necessary for the RFID labelantenna imaginary impedance Z to be in the range of +j (140 to 270) ohmsfor these two RFID devices to achieve resonance at the target frequency.

Therefore, a combination RFID/EAS security tag can be designed using theimpedance of the EAS component for matching purposes. In free space, theRFID component antenna can be designed to have a negative imaginaryimpedance and achieve the correct positive imaginary impedance whenplaced directly beneath, atop or nearby the EAS component. As can beappreciated by the present disclosure, this configuration may be usedwith any type of EAS tag or label, such as, for example, various typesof adhesive magnetostrictive labels and EAS hard tags, such as theSuperTag® produced by Sensormatic Corporation, a division of Tyco Fireand Security, LLC of Boca Raton, Fla. The types of EAS devices are notlimited to these specific examples.

The RFID component may include, for example, a semiconductor integratedcircuit (IC) and a tunable antenna. The tunable antenna may be tuned toa desired operating frequency by adjusting the length of the antenna.The range of operating frequencies may vary, although the embodimentsmay be particularly useful for ultra-high frequency (UHF) spectrum.Depending upon the application and the size of the area available forthe antenna, the antenna may be tuned within several hundred Megahertz(MHz) or higher, such as 868-950 MHz, for example. In one embodiment,for example, the tunable antenna may be tuned to operate within an RFIDoperating frequency, such as the 868 MHz band used in Europe, the 915MHz Industrial, Scientific and Medical (ISM) band used in the UnitedStates, and the 950 MHz band proposed for Japan. It is again noted thatthese operating frequencies are given by way of example only, and theembodiments are not limited in this context.

In one embodiment, for example, the tunable antenna may have a uniqueantenna geometry of an inwardly spiral pattern useful for RFIDapplications or EAS applications. The inwardly spiral pattern may nestthe antenna traces thereby bringing the traces back towards the origin.This may result in an antenna similar in functionality to that of aconventional half-wave dipole antenna, but with a smaller overall size.For example, the size of a conventional half-wave dipole antenna at 915MHz would be approximately 16.4 centimeters (cm) long. By way ofcontrast, some embodiments may offer the same performance as theconventional half-wave dipole antenna at the 915 MHz operating frequencywith a shorter length of approximately 3.81 cm. Furthermore, the ends ofthe antenna traces may be modified to tune the antenna to a desiredoperating frequency. Since the ends of the antenna traces are inwardfrom the perimeter of the antenna, the tuning may be accomplishedwithout changing the geometry of the antenna.

FIG. 3A shows a first system in accordance with one particularly usefulembodiment of the present disclosure. FIG. 3A shows an RFID system 100which may be configured to operate using RFID component 2 having anoperating frequency in the high frequency (HF) band which is consideredto be frequencies up to and including 30 MHz. In this frequency range,the primary component of the electromagnetic field is magnetic. RFIDsystem 100, however, may also be configured to operate RFID component 2using other portions of the RF spectrum as desired for a givenimplementation. The embodiments are not limited in this context. Asillustrated by way of example, RFID component 2 partially overlaps EAScomponent 1.

RFID system 100 may include a plurality of nodes. The term “node” asused herein may refer to a system, element, module, component, board ordevice that may process a signal representing information. The signaltype may be, for example but not limited to, electrical, optical,acoustical and/or a chemical in nature. Although FIG. 3A shows a limitednumber of nodes, it can be appreciated that any number of nodes may beused in RFID system 100. The embodiments are not limited in thiscontext.

Referring first to FIG. 4, FIG. 4 illustrates a side view for a securitytag 200 in accordance with one particularly useful embodiment of thepresent disclosure. RFID component 2 includes a base portion orsubstrate 202 having a first surface or surface area 202 a and a secondsurface or surface area 202 b which are typically on opposing sides ofbase portion or substrate 202. An antenna 204 is disposed on thesubstrate 202. The antenna 204 has a first surface or surface area 204 aand a second surface or surface area 204 b which are typically onopposing sides of antenna 204. A lead frame 206 is disposed on theantenna 204, and an application specific semiconductor integratedcircuit (ASIC) 208 is disposed on the lead frame 206. First and secondsurfaces or surface areas 202 a and 202 b, 204 a and 204 b are definedsurface areas of RFID component 2.

The security tag 200 includes a substantially planar covering materialor spacer 210 disposed on the RFID component 2 and EAS component 1disposed on the spacer 210. The spacer 210 has surfaces or surface areas210 a and 210 b disposed on opposite sides thereof.

EAS component 1 has a first surface or surface area 1 a and a secondsurface or surface area 1 b which are typically on opposing sides of EAScomponent 1. First and second surfaces or surface areas 1 a and 1 b aredefined surfaces or surface areas of EAS component 1.

For reference purposes, security tag 200 is illustrated as beingdisposed directly underneath EAS component 1, i.e., in position P4 ofFIG. 1. The security tag 200 is shown in position P4 by way of exampleonly and may be disposed in any position with respect to EAS label 1, asdiscussed previously with respect to FIG. 1. Security tag 200 may alsobe utilized completely independently of EAS label 1 or in conjunctiontherewith. The embodiments are not limited in this context.

More particularly, security tag 200 includes an EAS component 1 havingone of the defined surface areas 1 a and 1 b and an RFID component 2having one of the defined surface or surface areas 202 a, 202 b, 204 aand 204 b. At least one of the defined surface or surface areas 1 a and1 b of the EAS component 1 is configured to at least partially overlapat least one of the defined surface or surface areas 202 a, 202 b, 204 aand 204 b of the RFID component 2. The RFID component 2 may includeantenna 204 which at least partially overlaps at least one of thedefined surfaces or surface areas 1 a and 1 b of the EAS component 1.

In one embodiment, the defined surface or surface area of the RFIDcomponent 2 is one of surface or surface area 202 a and 202 b.

The substantially planar spacer 210 has a thickness “t” and is at leastpartially disposed between at least one of the defined surfaces orsurface areas 1 a and 1 b of the EAS component 1 and at least one of thedefined surfaces or surface areas 202 a, 202 b, 204 a, and 204 b of theRFID component 2.

Although FIG. 4 illustrates a limited number of elements, it may beappreciated that a greater or lesser number of elements may be used forsecurity tag 200. For example, an adhesive and release liner may beadded to security tag 200 to assist in attaching security tag 200 to anobject to be monitored. Those skilled in the art will recognize thatsemiconductor IC 208 may be directly bonded to antenna 204 without thelead frame 206.

Returning now to FIG. 3A, RFID system 100 may also include an RFIDreader 102 and security tag 200. Security tag 200 is physicallyseparated from RFID reader 102 by a distance d1. As is explained belowwith respect to FIG. 4, security tag 200 is an RFID security tag, tag orlabel which differs over the prior art in that it includes an EAScomponent, i.e., an EAS label or tag. RFID component 2 includes aresonant circuit 112. Resonant circuit 112 includes inductor coil L2with a resonating capacitor C2 across the terminals T1 and T2 of ASIC208. The capacitance of ASIC 208 is usually negligible compared to C2.If necessary to add additional capacitance to the resonant circuit 112to enable tuning the antenna, i.e., inductor coil 112, to the properfrequency, a capacitor C2 is connected in parallel to inductor coil L2so that resonant circuit 112 becomes a parallel resonant circuit havingterminals T1 and T2 across which an induced voltage V_(i) may be formed.As is explained below with respect to FIG. 4, terminals T1 and T2 arecoupled to other portions of the RFID component 2. In addition, theinductance value of inductor coil or antenna L2 includes the inductancepresented by the EAS label or tag.

RFID reader 102 may include a tuned circuit 108 having an inductor L1which serves as an antenna for RFID reader 102. Where necessary to addadditional capacitance to the tuned circuit 108 to enable proper tuningof the inductor coil or antenna L1, a capacitor C1 is connected inseries with inductor coil or antenna L1. RFID reader 102 is configuredto produce a pulsed or continuous wave (CW) RF power across the tunedcircuit 108 which is electro-magnetically coupled by alternating currentaction to parallel resonant circuit antenna 112 of RFID component 2. Themutually coupled electromagnetic power from RFID component 2 is coupledto RFID reader 102 through a magnetic field 114.

RFID component 2 is a power converter circuit that converts some of thecoupled CW RF electromagnetic power of magnetic field 114 into directcurrent signal power for use by the logic circuits of the semiconductorIC used to implement the RFID operations for RFID component 2.

RFID component 2 may also be a RFID security tag which includes memoryto store RFID information and which communicates the stored informationin response to an interrogation signal 104. RFID information may includeany type of information capable of being stored in a memory used by RFIDcomponent 2. Examples of RFID information include a unique tagidentifier, a unique system identifier, an identifier for the monitoredobject, and so forth. The types and amount of RFID information are notlimited in this context.

RFID component 2 may also be a passive RFID security tag. A passive RFIDsecurity tag does not use an external power source, but rather usesinterrogation signals 104 as a power source. A detection zone Z1 isdefined as an imaginary volume of space bounded by a generally sphericalsurface having a radius R1 generally originating from the inductor L1.The radius R1 defines a detection distance or read range R1 such that ifdistance d1 is less than or equal to read range R1, the RFID reader 102induces a required threshold voltage V_(T) across terminals T1 and T2 toactivate the RFID component 2. The read range R1 depends on, among otherfactors, the strength of the EM field radiation and magnetic field 114from the tuned circuit 208. Therefore, the strength of the EM fieldradiation 114 determines the read range R1.

RFID component 2 may be activated by a direct current voltage that isdeveloped as a result of rectifying the incoming RF carrier signalincluding interrogation signals 104. Once RFID component 2 is activated,it may then transmit the information stored in its memory register viaresponse signals 110.

In general high frequency (HF) operation, when resonant circuit 112 ofRFID system 100 is in proximity to tuned circuit 108 of RFID reader 102,an alternating current (AC) voltage V_(i) is developed across theterminals T1 and T2 of parallel resonant circuit 112 of RFID component2. The AC voltage V_(i) across resonant circuit 112 is rectified by arectifier to a direct current (DC) voltage and when the magnitude of therectified voltage reaches a threshold value V_(T), RFID component 2 isactivated. The rectifier is the aforementioned application specificintegrated circuit (ASIC) 208. Once activated, the RFID component 2sends stored data in its memory register by modulating interrogationsignals 104 of RFID reader 102 to form response signals 110. The RFIDdevice 106 then transmits the response signals 110 to the RFID reader102. RFID reader 102 receives response signals 110 and converts theminto a detected serial data word bitstream of data representative of theinformation from RFID component 2.

The RFID system 100 as illustrated in FIG. 3A may be considered to be ahigh frequency (HF) RFID system because the RFID reader 102 couplesinductively to the RFID component 2 via magnetic field 114. In HFapplications, antenna 204 is typically an inductance coil type antennaas provided by inductance coil L2.

FIG. 3B illustrates an ultrahigh frequency (UHF) RFID system 150 inwhich an RFID reader 152 couples to an RFID device, tag or label 156 ata distance d2 away via an electric field E. The frequency band for UHFis considered herein to range from about 300 MHz to about 3 GHz. The UHFrange specifically includes frequencies in the 868 MHz band, the 915 MHzband, and the 950 MHz band.

For UHF applications, antenna 204 of RFID component 2 typically-includesa UHF open-ended dipole antenna while the RFID reader 152 typicallyincludes a patch antenna. A coaxial feed line from the reader 152 isconnected to the patch antenna. The UHF antenna may be a simplehalf-wave dipole or a patch antenna. Many popular designs use an airfilled cavity backed patch antenna which can be either linearlypolarized or circularly polarized. The electric field vectors E1 and E2rotate with equal magnitude for the circularly polarized case. Thelinearly polarized antenna has higher magnitudes of E field in certainorthogonal orientations, which may be suitable for certain RFID labelorientations.

Therefore, in UHF applications, the antenna 204 of RFID component 2includes an open-ended dipole antenna while in HF applications, istypically inductor L2.

In general, when operating in the UHF range, it is not necessary for theRFID component 2 to include a capacitor such as C2 in parallel with theopen-ended dipole antenna 204 to enable tuning to the frequencytransmitted by the patch antenna of RFID reader 152.

Returning to FIG. 4, as previously noted, RFID component 2 may include abase portion or substrate 202 which includes any type of materialsuitable for mounting antenna 204, lead frame 206, and IC 208. Forexample, material for substrate 202 may include base paper,polyethylene, polyester, polyethyleneterephthalate (PET), polyetherimide(PEI) (e.g., ULTEM® amorphous thermoplastic PEI sold by the GeneralElectric Co. of Fairfield, Conn.) and/or other materials. It is knownthat the particular material implemented for substrate 202 may impactthe RF performance of security tag 200 and, as such, the dielectricconstant and the loss tangent may characterize the dielectric propertiesof an appropriate substrate material for use as substrate 202.

In general, a higher dielectric constant may cause a larger frequencyshift of an antenna when compared to free space with no substratepresent. Although it may be possible to re-tune the antenna to theoriginal center frequency by physically changing the antenna pattern, itmay be desirable to have a material with a high dielectric constant andwith a low dielectric loss since usage of such a material results in asmaller tag or label size. The term “read range” may refer to thecommunication operating distance between RFID reader 102 and securitytag 200. An example of a read range for security tag 200 may range from1-3 meters, although the embodiments are not limited in this context.The loss tangent may characterize the absorption of RF energy by thedielectric. The absorbed energy may be lost as heat and may beunavailable for use by ASIC 208. The lost energy may result in the sameeffect as reducing the transmitted power and may reduce the read rangeaccordingly. Consequently, it may be desirable to have the lowest losstangent possible in substrate 202 since it cannot be “tuned out” byadjusting antenna 204. The total frequency shift and RF loss may dependalso on the thickness of substrate 202. As the thickness increases, theshift and loss may also increase.

In one embodiment, for example, substrate 202 may be configured usingbase paper having a dielectric constant of about 3.3, and a loss tangentof about 0.135. The base paper may be relatively lossy at 900 MHz. Alossy material has a dielectric loss factor greater than about 0.01. Inone embodiment, substrate 202 may be configured of plastic having adielectric constant of about 3.3 and a loss tangent of less than about0.01. The embodiments are not limited in this context.

In one embodiment, security tag 200 may include IC 208 having asemiconductor IC, such as an RFID chip or application specificintegrated circuit (ASIC) (“RFID chip”). RFID chip 208 may include, forexample, an RF or alternating current (AC) rectifier that converts RF orAC voltage to DC voltage, a modulation circuit that is used to transmitstored data to the RFID reader, a memory circuit that storesinformation, and a logic circuit that controls overall function of thedevice. In one embodiment, RFID chip 208 may be configured to use anI-CODE High Frequency Smart Label (HSL) RFID ASIC or a U-CODE UltrahighFrequency Smart Label (USL) RFID ASIC, both of which are made by PhilipsSemiconductor of Amsterdam, the Netherlands, or an XRA00 RFID chip madeby ST Microelectronics of Geneva, Switzerland. The embodiments, however,are not limited in this context.

Lead frames are small connections which enable attaching an RFID chipsuch as RFID chip 208 to an antenna such as antenna 204. In oneembodiment, RFID chip 208 may be directly bonded to antenna 204 withoutincluding lead frame 206. Lead frame 206 may also include a die mountingpaddle or flag, and multiple lead fingers. The die paddle primarilyserves to mechanically support the die during package manufacture. Thelead fingers connect the die to the circuitry external to the package.One end of each lead finger is typically connected to a bond pad on thedie by wire bonds or tape automated bonds. The other end of each leadfinger is the lead, which is mechanically and electrically connected toa substrate or circuit board. Lead frame 206 may be constructed fromsheet metal by stamping or etching, often followed by a finish such asplating, downset and taping. In one embodiment, for example, lead frame206 may be implemented using a Sensormatic EAS Microlabel™ lead framemade by Sensormatic Corporation, a division of Tyco Fire and Security,LLC, of Boca Raton, Fla., for example. The embodiments, however, are notlimited in this context.

In one embodiment, antenna 204 includes the inductor coil L2, and whenrequired, the capacitor C2, of resonant circuit 112 of RFID component 2.The terminals T1 and T2 are also included in antenna 204 to couple tothe RFID chip 208 to enable the induced voltage V_(i) to activate theRFID component 2 once the threshold voltage V_(T) is reached.

In one embodiment, antenna 204 includes typically the open ended dipoleantenna of RFID component 2 for UHF applications. Terminals T1 and T2may also be included in antenna 204 to couple to the RFID chip 208 toenable the electric field E to excite the antenna of reader 152

In one embodiment, security tag 200 may also include covering or spacermaterial 210 applied to the top of a finished security tag. As withsubstrate 202, covering or spacer material 210 may also impact the RFperformance of RFID component 2. For example, covering material 210 maybe implemented using cover stock material having a dielectric constantof about 3.8 and a loss tangent of about 0.115. The embodiments are notlimited in this context.

More particularly, as previously mentioned, the substantially planarspacer 210 has a thickness “t”. The thickness “t” is generally about 1mm to 2 mm when the security tag 200 is a hard combination tag andconsiderably less than 1 mm when the security tag 200 is a combinationlabel. As previously mentioned, the spacer 210 has surfaces or surfaceareas 210 a and 210 b disposed on opposite sides thereof. In oneembodiment, spacer surfaces or surface areas 210 a and 210 b areparallel to each other. EAS component 1 at least partially overlaps atleast one of the spacer surfaces or surface areas 210 a and 210 b.

An RFID insert is a term common in the art and may be defined herein asthe RFID component 2, which includes the combination of substrate 202,antenna 204, lead frame 206 if applicable, and RFID chip 208. RFIDcomponent 2 at least partially overlaps another one of the spacersurfaces 210 b. Security tag 200 includes RFID insert or component 2 andspacer 210.

Security tag 200 may also include antenna 204. Antenna 204 may berepresentative of, for example, antenna 112 of RFID device 106 orantenna 204 may be formed by a parallel resonant LC circuit, where L isinductance and C is capacitance. Alternatively, antenna 204 may also bea tunable antenna which is tuned to the carrier signal so that thevoltage across the antenna circuit is maximized. As can be appreciatedthis will increase the read range of antenna 204. It is known that thedegree of preciseness of the tuning circuit is related to the spectrumwidth of the carrier signal transmitted by transmitter 102. For example,in the United States, the Federal Communication Commission currently(FCC) regulates one band of the RFID security tag spectrum to 915 MHz.Therefore, transmitter 102 should transmit interrogation signals 104 atapproximately 915 MHz. To receive interrogation signals 104, antenna 204should be narrowly tuned to the 915 MHz signal. For 915 MHzapplications, the RFID tag antenna 204 may be printed, etched or plated.

The EAS label 1 creates or presents a constant load impedance to RFIDcomponent 2. As a result, antenna 204 of RFID label 200 uses thisconstant load of EAS label 1 for impedance matching. More particularly,antenna 204 has a complex impedance and the EAS component 1 forms a partof an impedance matching network of the antenna. Therefore, theimpedance of antenna 204 includes the loading effect of the EAScomponent 1. That is, the loading effects of the EAS component 1 are theconstant load impedance of the EAS component 1. The loading effect ofEAS component 1 may be varied by substituting or exchanging one materialincluded within the EAS component 1 having one dielectric constant andloss tangent for another material having another dielectric constant andloss tangent.

The RFID component chip 208 may be represented as an equivalent seriesRC circuit, where R represents a resistor and C represents a capacitor.This circuit is represented by a complex impedance Z_(chip) asZ _(chip) =Z ₁ −jZ ₂,

where Z₁ and Z₂ are the real and imaginary components of the impedanceof the chip 208. The RFID device tag or label antenna 204 may berepresented by a complex impedance Z_(antenna) asZ _(antenna) =Z ₃ −jZ ₄  (1)

where Z3 and Z4 are the real and imaginary components of the impedanceof the antenna 204. When the chip 208 is mounted on the antenna 204, thecomplex impedance of chip 208 is matched to the coupled conjugateimpedance of the RFID antenna 204, including the impedance matchingeffect or loading effect of the EAS component or label 1. This allowsmaximum power coupling to the RFID chip 208 which results in thegreatest read range R1.

In one embodiment, thickness “t” of spacer 210 may be varied to varywith respect to either the RFID reader device 102 or to the RFID readerdevice 152 in order to vary the read range R1, respectively. Moreparticularly, thickness “t” determines the read range, i.e., the maximumdistance R1 between the security tag 200 and the EAS/RFID reader 102 orthe EAS/RFID reader 152 at which the reader 102 or 152 may interrogatethe security tag 200. The read range R1 is affected adversely asthickness “t” decreases. Conversely, the read range R1 increases asthickness “t” increases. It should be noted that reader 102 for HFapplications and reader 152 for UHF either read only the EAS component 1or only the RFID component 2 such that the EAS component 1 is read by adedicated EAS reader while RFID component 2 is read by a dedicated RFIDreader. Alternatively, reader 102 and reader 152 may be combined in thesame housing or their functions integrated to be performed by the samehardware. Undesirable interference between the reading of EAS component1 and the reading of RFID component 2 is prevented or minimized becauseof the wide discrepancy between the range of read frequencies common toEAS components as opposed the range of read frequencies common to RFIDcomponents, with the EAS components typically being read at frequenciesin the range of less than or equal to 8.2 KHz, whereas RFID componentsare typically being read at frequencies in the range of 13 MHz orgreater.

However, it is envisioned that since security tags 200 and 400 are standalone devices, security tags 200 and 400 provide an EAS function and anRFID function independently of the type of reader or readers orparticular frequencies to which security tags 200 or 400 are subjected.

The spacer 210 is made using a low loss, low dielectric material such asECCOSTOCK® RH rigid foam, made by Emerson Cuming Microwave Products,Inc. of Randolph, Mass., or any other similar material. The embodimentsare not limited in this context. When made from one of the foregoingmaterials, the read range is about 30.5 to 61.0 cm (1 to 2 feet) whenthe thickness “t” of spacer 902 is about 0.0762 mm (0.003 inches).Similarly, the read range is about 127 cm (5 feet) when the thickness“t” of spacer 210 is at least 1.02 mm (0.040 inches).

In one embodiment, the spacer 210 may be a thin film having a thickness“t” of about 0.05 mm where EAS component 1 directly overlaps RFIDcomponent 2.

In one embodiment, the spacer may be air where the EAS label 1 issupported mechanically away from the RFID component 2.

As a result, security tag 200 provides significant advantages over theprior art by enabling a combined EAS/RFID devices of significantly lowerspace or volume and lower cost.

In one embodiment, security tag 200 may use an induced voltage from acoil antenna for operation. This induced AC voltage may be rectified toresult in a DC voltage. As the DC voltage reaches a certain level, theRFID component 2 begins operating. By providing an energizing RF signalvia transmitter 102, RFID reader 102 can communicate with a remotelylocated security tag 200 that has no external power source such as abattery.

Since the energizing and communication between the RFID reader and RFIDcomponent 2 is accomplished through antenna 204, antenna 204 may betuned for improved RFID applications. An RF signal can be radiated orreceived effectively if the linear dimension of the antenna iscomparable with the wavelength of the operating frequency. The lineardimension, however, may be greater than the available surface areaavailable for antenna 204. Therefore, it may prove difficult to utilizea true full size antenna in a limited space which is true for most RFIDsystems in HF applications. Accordingly, it is contemplated that RFIDcomponent 2 may use a smaller LC loop antenna circuit that is arrangedto resonate at a given operating frequency. The LC loop antenna mayinclude, for example, a spiral coil and a capacitor. The spiral coil istypically formed by n-turns of wire, or n-turns of a printed or etchedinductor on a dielectric substrate.

For HF applications, in order to achieve good RFID coupling, the looparea*turns product and resonant frequency need to be optimized. In oneembodiment of the present disclosure illustrated in FIG. 3A, theresonant frequency can be effected by tuning the parallel capacitor C2of the resonant circuit 112 including the effects on impedance of theEAS label 1 and of the RFID chip 208.

In either HF or UHF applications, for the particular frequency ofinterest, the RFID chip complex impedance must be matched by the complexconjugate impedance of the antenna including the loading effects onimpedance of the EAS label. In the HF case, a resonating capacitor iscommonly used to tune the frequency. This capacitor is usually largerthan the RFID chip capacitance and will dominate the response. For theUHF case, the RFID chip complex impedance contains only the chipcapacitance for tuning.

In another embodiment according to the present disclosure, antenna 204may be designed so that the complex conjugate of the overall antennamatches the impedance to the complex impedance of lead frame 206 and IC208 at the desired operating frequency, e.g., 915 MHz. When RFIDsecurity tag 200 is placed on an object to be monitored, however, it hasbeen observed that the resulting operating frequency may change, i.e.,each object may have a substrate material with dielectric propertiesaffecting the RF performance of antenna 204. In other words and as withsubstrate 202, the object substrate may cause frequency shifts and RFlosses determined by the dielectric constant, loss tangent, and materialthickness. Examples of different object substrates may include so called“chip board” (i.e., material used for item-level cartons, corrugatedfiber board which is material used for corrugated boxes), video cassetteand digital video disc (DVD) cases, glass, metal, etc. It iscontemplated that each object substrate may have a significant effect onthe read range R1 for security tag 200.

Antenna 204 may be tunable to compensate for such variations. In otherwords, since the dielectric constant for many materials is greater thanone, the operating frequency is typically lowered when security tag 200is attached to an object substrate. In order to establish the originalfrequency, antenna 204 is typically altered in some manner, otherwisedetection performance and read range may be reduced. As such, antenna204 may be altered by trimming the ends of antenna 204 by severing theantenna conductor and isolating the resultant trimmed antenna segmentfrom the ends that were cut away. The trimmed ends do not necessarilyhave to be removed to allow the tuning operation. Consequently,continuous tuning of antenna 204 to the desired operating frequency ispossible to allow operation of security tag 200 when security tag 200 isattached to different objects. Security tag 200 in general, and antenna204 in particular, are described in more detail below with reference toFIGS. 5-7.

FIG. 5 illustrates a top view of a partial security tag 200 with anantenna in accordance with one embodiment according to the presentdisclosure which is particularly suitable for UHF applications. Securitytag 200 includes antenna 204 disposed upon substrate 202 which issubstantially rectangular in shapes. In one envisioned embodiment,antenna 204 is disposed on substrate 202 by die-cutting the labelantenna pattern onto substrate 202.

RFID chip 208 may be connected to lead frame 206 by ultrasonicallybonding lead frame 206 to the conductive pads on RFID chip 208. In theparticular embodiment of FIG. 5, RFID chip 208 and lead frame 206 areplaced in the geometric center of the dielectric substrate material ofsubstrate 202. The ends of lead frame 206 are mechanically andelectrically bonded to the foil antenna pattern of antenna 204. Coveringmaterial 210 (not shown) is applied over the entire top surface ofsecurity tag 200 to protect the assembly and provide a surface forprinting indicia if desired. It is known in the art to use ananisotropic electrically conductive thermally setting adhesive to bondthe RFID chip 208 to the antenna 204. An example of such an adhesive isLoctite 383® made by the Henkel Loctite Corporation of Rocky Hill, Conn.Antenna 204 may also include multiple antenna portions. For example,antenna 204 may include a first antenna portion 306 and a second antennaportion 308, the first antenna portion 306 being connected to a firstside 206A of lead frame 206, and the second antenna portion 308connected to a second side 206B of lead frame 206. Therefore, antenna204 is the entire RFID tag antenna which is subdivided into firstantenna portion 306 and second antenna portion 308.

First antenna portion 306 may have a first antenna end 306A and a secondantenna end 306B. Similarly, second antenna portion 308 may have a firstantenna end 308A and a second antenna end 308B. In one embodiment and asshown in FIG. 5, first antenna end 306A of first antenna portion 306 isconnected to lead frame 206A. First antenna portion 306 is disposed onsubstrate 202 to form an inwardly spiral pattern from RFID chip 208 in afirst direction, with second antenna end 306B positioned to terminate onthe inner loop of the inwardly spiral pattern. Similarly, first antennaend 308A of second antenna portion 308 may be connected to lead frame206B. Second antenna portion 308 is also disposed on substrate 202 toform an inwardly spiral pattern from RFID chip 208 in a seconddirection, with second antenna end 308B positioned to terminate on theinner loop of the inwardly spiral pattern.

In one embodiment, the antenna geometry of antenna 204 is configured totraverse around the perimeter of substrate 202 and spiral inwardly. Itis envisioned that the inwardly directed spiral antenna pattern mayprovide several advantages:

(1) The ends of antenna 204 may be placed well inside the perimeter ofsubstrate 202. Placing the ends of antenna 204 within the perimeter ofsubstrate 202 may allow the ends to be trimmed without changing theamount of area used by antenna 204;

(2) The Q factor of antenna 204 may be optimized so that the response ofsecurity tag 200, including the effects of spacer 210 and EAS label 1,only varies by approximately −3 dB at the ISM band limits. Using theChu-Harrington limit of Q=1/(ka)³+1/(ka), where k=2π/λ and “a” is acharacteristic dimension of antenna 204, it can be seen that a sphere ofradius “a” could just enclose security tag 200. For a high Q factor,then “ka” should be <<1. Therefore, by maximizing Q, “a” is minimized tofall within the operating frequency band limits. The tuning of antenna204 for UHF applications is disclosed in further detail in co-pending,commonly owned U.S. patent application Ser. No. 10/917,752 filed on Aug.13, 2004 entitled “TUNABLE ANTENNA” by R. Copeland and G. M. Shafer.

Antenna 204 may also be tuned particularly for UHF applications to adesired operating frequency by modifying a first length for firstantenna portion 306, and a second length for second antenna portion 308,after these antenna portions are disposed on substrate 202. For example,each antenna portion may be divided into multiple antenna segments atmultiple segment points. The first and second antenna lengths may bemodified by electrically isolating at least a first antenna segment froma second antenna segment. The antenna length may be modified by severingeach antenna portion at one of multiple segment points, with eachsegment point to correspond to an operating frequency for antenna 204.Dividing first antenna portion 306 and second antenna portion 308 intomultiple antenna segments results in shortening the length of eachantenna portion, and thereby effectively changes the total inductance ofantenna 204. The antenna segments and segment points are described inmore detail with reference to FIG. 6.

FIG. 6 illustrates a diagram of a security tag 400 with an antennahaving segment points in accordance with one embodiment. In particular,FIG. 6 illustrates a top view of portions of security tag 400 withmultiple segment points SP1, SP2, SP3 and SP4. In a similar manner asshown in FIG. 4 with respect to security tag 200, security tag 400 mayinclude EAS component 1, spacer 210 and RFID component 2. Antenna 204may be tuned also to a desired operating frequency by modifying a firstlength for first antenna portion 306, and a second length for secondantenna portion 308, after these antenna portions are disposed onsubstrate 202. For example, it is contemplated that each antenna portionmay be divided into multiple antenna segments at multiple segment pointsSP1-SP4. Multiple segment points SP1 through SP4 represent end tuningpositions where the antenna 204 may be cut or trimmed in order to betuned to various objects. SP1 is the free space position where thelength of original free space antenna 204 is tuned to 868 MHz. SP2 isthe free space position where the length of antenna portions 306 and 308is tuned to 915 MHz. SP3 and SP4 are the free space positions where thelength of antenna portions 306 and 308 is tuned to the various objects.The various objects include, for example and are not limited to, retailand/or wholesale merchandise.

The first and second antenna lengths may be modified by electricallyisolating at least a first antenna segment from a second antennasegment. The antenna length may be modified by severing each antennaportion at one of multiple segment points, with each segment tocorrespond to an operating frequency for antenna 204. The severing maybe achieved in a number of different ways, such as cutting or punchingthe antenna trace at a given segment point SP1-SP4. The severing maycreate a slot at the segment point, such as slots 402, 404, 406, 408,410, and 412.

It should be noted that for HF applications, antenna 204 is tuned bychanging the inductance or capacitance parameters but not the lengths ofthe segments.

In one embodiment, and as shown in FIG. 6, each segment point SP1-SP4corresponds to an operating frequency for antenna 204. In one example,SP1 may tune antenna 204 for an operating frequency of approximately 868MHz when security tag 400 is in free space and unattached to an object.SP2 may tune antenna 204 for an operating frequency of approximately 915MHz when security tag 400 is in free space and unattached to an object.SP3 may tune antenna 204 for an operating frequency of approximately 915MHz when security tag 400 is attached to a VHS cassette housing. SP4 maytune antenna 204 for an operating frequency of approximately 915 MHzwhen—security tag 400 is attached to a chip board. As can beappreciated, the number of segment points and corresponding operatingfrequencies for antenna 204 may vary according to a givenimplementation. The embodiments are not limited in this context.

FIG. 7 illustrates a block flow diagram 500 in accordance with anotherembodiment of the present invention. As mentioned above, security tag200 may be configured in a number of different ways. For example: 1) anintegrated circuit may be connected to a lead frame at block 502; 2) anantenna may be disposed on a substrate at block 504; 3) the lead framemay be connected to the antenna at block 506.

In one particular embodiment, the antenna is tuned for use with anoperating frequency at block 508. The tuning may be performed bymodifying a length for the antenna by severing the antenna into multipleantenna segments at a segment point corresponding to the operatingfrequency. The severing may electrically disconnect a first antennasegment from a second antenna segment, thereby effectively shorteningthe length of the antenna.

As described above, the unique antenna geometry of an inwardly spiralpattern may be useful for RFID applications when connected to an RFIDchip. As previously noted, the unique antenna geometry shown in FIGS. 5and 6, however, may also be useful for an EAS system where security tag200 and security tag 400, respectively, each include EAS component 1 andspacer 210. In one embodiment, RFID chip 208 may be replaced with adiode or other non-linear passive device where the voltage and currentcharacteristics are non-linear. The antenna for the diode or otherpassive non-linear EAS device may have the same geometry as shown inFIGS. 5 and 6, and may be trimmed to tune the antenna to the operatingfrequency of the transmitter used to transmit interrogation signals forthe EAS system. Similar to RFID system 100, the range of operatingfrequencies may vary, although the embodiments may be particularlyuseful for the UHF spectrum, such as 868-950 MHz. The embodiments arenot limited in this context.

It is also contemplated that some embodiments of the present disclosuremay be configured using an architecture that may vary in accordance withany number of factors, such as: 1) desired computational rate; 2) powerlevels; 3) heat tolerances; 4) processing cycle budget; 5) input datarates; 6) output data rates; 7) memory resources; 8) data bus speeds andother performance constraints. For example, an embodiment may beconfigured using software executed by a general-purpose orspecial-purpose processor. In another example, an embodiment may beconfigured as dedicated hardware, such as a circuit, an ASIC,Programmable Logic Device (PLD) or a digital signal processor (DSP). Inyet another example, an embodiment may be configured by any combinationof programmed general-purpose computer components and custom hardwarecomponents. The embodiments are not limited in this context.

Examples of security tags 200 and 400, which are combination EAS andRFID labels/tags, are shown in FIGS. 8A to 8D which show various typesof adhesive magnetostrictive labels and EAS hard tags, such as theSuperTag® produced by Sensormatic, a division of Tyco Fire and Security,LLC of Boca Raton, Fla. FIG. 8A illustrates an EAS label 804 adjacent toan RFID label 806 in a co-planar configuration. This configuration ofadjacent labels 804 and 806 is known in the prior art. FIG. 8Billustrates a variation of the co-planar configuration of EAS label 804and RFID label 806 of FIG. 8A wherein the EAS label 804 and the RFIDlabel 806 are separated from each other by a gap 805 having a distance“g”. This configuration of 804 and 806 being separated by gap 805 isalso known in the prior art.

In both the configuration of FIGS. 8A and 8B, the EAS label 804 and theRFID label 806 act independently of one another with respect to matchingof impedance values. As “g” increases, the read range increases. As aresult, the size of gap “g” controls the impedance load. However, thisis not a desirable effect because although the read range increases, thetotal area occupied by the EAS label 804 and RFID label 806 increases,necessarily occupying more space or area on an object to be identified.

FIG. 8C illustrates an embodiment of the present disclosure of asecurity tag 200 or 400 showing an EAS component or label 1. An RFIDcomponent or insert 2 is mounted directly underneath the EAS componentor label 1. A dummy bar code 802 is printed on the EAS component orlabel 1 and is just for visual purposes only. Dummy bar code 802 has noEAS or RFID function. As compared to the prior art, the configuration ofsecurity tag 200 or 400 as a combination EAS component or label or tag 1with RFID component or insert 2 mounted directly underneath the EAScomponent or label 1 (as shown in FIG. 4) provides a minimal separationbetween the RFID component or insert 2 and the EAS label 1.

FIG. 8D illustrates one embodiment of the present disclosure of oneportion 812 of a housing for combination EAS component or label 1 withRFID component or insert 2. The RFID component or insert 2 is defined asincluding RFID chip 208 mounted on antenna 204. However, spacer 210 oran adhesive layer are not visible (See FIG. 4).

FIG. 8E is an elevation view of the combination EAS component or label 1with RFID component or insert 2 disclosed in FIG. 8D, but showing spacer210 disposed between the EAS component or label 1 and the RFID componentor insert 2.

FIG. 8F illustrates one embodiment of the present disclosure of oneportion 818 of a housing for a combination EAS label 816 similar to EAScomponent or label 1 with an RFID insert 814 which is similar to RFIDcomponent or insert 2. The RFID insert 814 is defined as another RFIDchip 820 mounted on antenna 204. Again, spacer 210 or an adhesive layerare not visible (See FIG. 4).

FIG. 8G is an elevation view of the combination EAS label 816 with RFIDinsert 814 disclosed in FIG. 8F, but showing spacer 210 disposed betweenthe EAS label 816 and the RFID insert 814.

FIG. 9 illustrates another embodiment of the invention. In FIG. 9, acombination EAS/RFID security tag includes a hybrid antenna inlay 900having two inward spiral antennas 910 and 920, as well as a rectangularmagnetic loop antenna 930 coupled to the inward spiral antennas 910 and920. RFID chip 940 is electrically connected to magnetic loop antenna930 and magnetic loop antenna 930 is then electrically connected to theinward spiral antennas 910 and 920 as shown in FIG. 9. In a particularnon-limiting example, the Impinj Gen. 2 Monza RFID chip is used. Theoverall geometry of magnetic loop antenna 930 is such that the nearfield magnetic H performance is optimized. Spiral antennas 910 and 920dominate the far field response.

Magnetic loop antenna 930 also acts as a means to reduce ESD damage toRFID chip 940. For low frequency or static electric E fields produced bymanufacturing processes or ultrasonic welding of the hard tag housing,the magnetic loop antenna 930 is essentially a short circuit across RFIDchip 940. If an electrical discharge initiates from one end of spiralantenna 910 to the end of spiral antenna 920, for example, loop antenna930 diverts the discharge current away from RFID chip 940.

Physically, the spiral antennas 910 and 920 are connected to magneticloop antenna 930 and not directly to RFID chip 930. When an E field isapplied along the length of the hybrid spiral/loop antenna inlay shownin FIG. 9, the current starts at the end of spiral antenna 910 (the leftspiral in FIG. 9) at low levels and gradually increases to theconnection point of the magnetic loop antenna 930. This current sense iscounterclockwise. The current through magnetic loop antenna 930 is alsoof a counterclockwise sense but at much larger values. The current fromthe magnetic loop connection point to the right side spiral antenna 920is of a counterclockwise sense and gradually decreases toward the end ofthis antenna trace. Thus, the direction of the currents in each spiralantenna 910 and 920 are the same.

The hybrid antenna inlay 900 shown in FIG. 9 is then placed inside ofthe housing of the hybrid EAS/RFID tag which contains the EAS element, aspacer, and an attachment clamp mechanism. The EAS/RFID security tagutilizing the hybrid antenna inlay 900 of FIG. 9 can be read by anyconventional RFID reader.

An example of a near field reader magnetic H field loop antenna usedwith the present invention is a 2 cm. diameter circular loop using astep-down transformer at the feed end of the loop, two tuning capacitorsat the halfway point, and a terminating resistor at the opposite end ofthe loop. However, the invention is not limited to a particular diameteror type of near field reader magnetic loop antenna. Near field magneticloop antenna 930 may also include a cylindrical slug of ferritematerial.

FIG. 9A shows the RFID read performance characteristics for the hybridantenna inlay 900 of FIG. 9 and the prior art antenna inlay as afunction of tag displacement from the inlay center relative to that ofthe center of the reader near field magnetic loop antenna. As can beobserved in FIG. 9B, using the hybrid antenna inlay 900 provides asuperior read distance compared to the prior art spiral antenna inlayabove the antenna and also provides an abrupt read region (the extent ofinlay displacement from the center of the antenna).

Using the hybrid antenna inlay 900 with the combination EAS/RFID tag notonly provides the same far field read performance as a pure spiralantenna, but also provides an improved near field magnetic response. Fora given overall size of hybrid antenna inlay 900, the ratio of thespiral antenna regions to that of the magnetic loop antenna regionshould be maintained. FIG. 9B illustrates these antenna regions.

In FIG. 9B, region 1 represents the region for magnetic loop antenna930, while regions 2 and 3 represent the right hand side and left handside of the inward spiral antennas 920 and 910 respectively. In oneembodiment, in order to achieve the same far field response as a spiralantenna, the hybrid antenna inlay 900 has a substantially similar arearatio for all three regions. For example, if the area of region 1 issubstantially smaller than regions 2 and 3, the far field response maybe the same as that of the spiral but may not optimize the near fieldmagnetic response. If region 1 becomes substantially larger than regions2 and 3, for a given overall size of inlay 900, there may not enoughspace for the spiral antenna traces to operate in the UHF region whenplaced inside of a combination EAS/RFID security tag.

The types of EAS devices and RFID combinations are not limited to theEAS and RFID devices described herein.

The present disclosure advantageously provides a hybrid antenna inlayfor use in an EAS/RFID security system, where the hybrid antenna inlayincludes an RFID spiral antenna having two components and a magneticloop antenna situated between the two spiral antenna components. Thehybrid antenna inlay design of the present disclosure maintains the farfield response abilities of the spiral antenna while increasing the nearfield magnetic performance due to the magnetic loop antenna. Further,the hybrid antenna inlay reduces ESD damage to the RFID integratedcircuit by diverting current away from the IC.

While certain features of the embodiments have been illustrated asdescribed herein, many modifications, substitutions, changes andequivalents will now occur to those skilled in the art. It is thereforeto be understood that the appended claims are intended to cover all suchmodifications and changes as fall within the true spirit of theembodiments.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention, which is limited only by the following claims.

1. A security tag comprising: an electronic article surveillance (EAS)component having a first defined surface area; and a radiofrequency(RFID) component having a second defined surface area, the RFIDcomponent including a hybrid antenna inlay comprising: an inward spiralantenna; a magnetic loop antenna in electrical contact with the spiralantenna; and an integrated circuit in electrical contact with themagnetic loop antenna.
 2. A security tag of claim 1, further comprisinga substantially planar spacer at least partially disposed between thefirst defined surface area of the EAS component and the second definedsurface area of the RFID component.
 3. The security tag of claim 1,wherein the integrated circuit is an application specific integratedcircuit (ASIC), the ASIC having a complex impedance.
 4. The security tagof claim 1, wherein the spiral antenna has a first section and a secondsection, wherein the magnetic loop antenna is positioned between thefirst section and the second section of the spiral antenna.
 5. Thesecurity tag of claim 4, wherein the first section of the spiral antennahas a third defined area, the second section of the spiral antenna has afourth defined area, and the magnetic loop antenna has a fifth definedarea, the third defined area of the first section of the spiral antenna,the fourth defined area of the second section of the spiral antenna andthe fifth defined area of the magnetic loop antenna being substantiallyequal.
 6. The security tag of claim 1, wherein the RFID component isactivatable when the RFID component is within a read range.
 7. Thesecurity tag of claim 4, wherein currents in the first and the secondsections of the spiral antenna flow in a same direction.
 8. The securitytag of claim 1, wherein the magnetic loop antenna is a near fieldmagnetic H field antenna.
 9. An RFID antenna inlay for use with acombination EAS/RFID security tag, the antenna inlay comprising: aninward spiral antenna having a first section and a second section; amagnetic loop antenna in electrical contact with the spiral antenna andbeing positioned between the first section of the spiral antenna and thesecond section of the spiral antenna; and an integrated circuit inelectrical contact with the magnetic loop antenna.
 10. The RFID antennainlay of claim 9, wherein the integrated circuit is an applicationspecific integrated circuit (ASIC), the ASIC having a complex impedance.11. The RFID antenna inlay of claim 9, wherein the first section of thespiral antenna has a first defined area, the second section of thespiral antenna has a second defined area, and the magnetic loop antennahas a third defined area, the first defined area of the first section ofthe spiral antenna, the second defined area of the second section of thespiral antenna and the third defined area of the magnetic loop antennabeing substantially equal.
 12. The RFID antenna inlay of claim 9,wherein currents in the first and the second sections of the spiralantenna flow in a same direction.
 13. The RFID antenna inlay of claim 9,wherein the magnetic loop antenna is a near field magnetic H fieldantenna.
 14. A method for providing an enhanced read response for asecurity tag, the method comprising: providing an electronic articlesurveillance (EAS) component having a first defined surface area;positioning a radiofrequency (RFID) component having a second definedsurface area to at least partially overlap the EAS component; the RFIDcomponent including a hybrid antenna inlay, the antenna inlaycomprising: an inward spiral antenna; a magnetic loop antenna inelectrical contact with the spiral antenna; and an integrated circuit inelectrical contact with the magnetic loop antenna.
 15. The method ofclaim 14, wherein the RFID component is activatable when the RFIDcomponent is within a read range.
 16. The method of claim 14, whereinthe spiral antenna has a first section and a second section, the methodfurther comprising positioning the magnetic loop antenna between thefirst section and the second section of the spiral antenna.
 17. Themethod of claim 16, the first section of the spiral antenna has a thirddefined area, the second section of the spiral antenna has a fourthdefined area, and the magnetic loop antenna has a fifth defined area,the third defined area of the first section of the spiral antenna, thefourth defined area of the second section of the spiral antenna and thefifth defined area of the magnetic loop antenna are substantially equal.18. The method of claim 16, wherein current in the first and the secondsections of the spiral antenna flow in the same direction.
 19. Themethod of claim 14, the magnetic loop antenna being a near fieldmagnetic H field antenna.